Fatty acids are broken down to :

Options

A. pyruvate molecules, which take electrons to the electron transport system
B. amino acids, which excrete ammonia
C. acetyl groups, which enter the Krebs cycle
D. all of the above

Explanation

### Step-by-Step Solution:

1. **Understanding Fatty Acid Breakdown**: Fatty acids are long-chain hydrocarbons that are broken down through a process called beta-oxidation. This process occurs in the mitochondria of cells.

2. **Triglyceride Hydrolysis**: Fatty acids are derived from triglycerides, which are broken down into fatty acids and glycerol through a process known as hydrolysis.

3. **Beta-Oxidation Process**: Once fatty acids are released, they undergo beta-oxidation. This process involves the sequential removal of two-carbon units from the fatty acid chain.

4. **Formation of Acetyl Coenzyme A**: The end product of beta-oxidation is acetyl CoA (acetyl coenzyme A). Each cycle of beta-oxidation produces one molecule of acetyl CoA.

5. **Entry into Krebs Cycle**: The acetyl CoA produced from fatty acid breakdown enters the Krebs cycle (also known as the citric acid cycle) where it is further oxidized to produce energy.

6. **Other Products**: In addition to acetyl CoA, beta-oxidation can also generate other products such as NADH and FADH2, which are important for the electron transport chain.

7. **Conclusion**: Therefore, the main product of fatty acid breakdown is acetyl CoA, which is utilized in the Krebs cycle.

### Final Answer:
Fatty acids are broken down to **acetyl groups (acetyl CoA)**, which enter the Krebs cycle.

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